In a conventional circular sliver knitting machine, the knitting machine drive mechanism imparts tremendous forces onto the sliver feed assemblies which card and feed sliver fiber into the knitting needles. The sliver feed assemblies are mounted in surrounding relation to the needle cylinder and are connected to a ring gear supported in a mounting channel of the upper bed plate. The ring gear is slidable on a mounting ring fixed in the mounting channel.
As the ring gear turns, the sliver feed assemblies are actuated for carding and feeding sliver into the knitting needles. Compared to a conventional circular knitting machine, the knitting needles in a sliver knitting machine move a more extended distance because the knitting needles must extend vertically into the doffing roll of the sliver feed assemblies. At the same time, the ring gear must rotate with precision in a circular pattern to ensure that the forces generated on each of the sliver feed assemblies is substantially equal. Any bearing assembly positioned between the ring gear and mounting ring not only must maintain ring gear movement in a circular pattern, but also must withstand the tremendous forces generated during knitting.
Because of the large diameter of most sliver knitting machines, conventional two-point contact ball bearing assemblies having inner and outer races have not been used between the ring gear and mounting ring of these machines. The bearing assembly between the ring gear and mounting ring requires a small cross section, and manufacturers find it difficult and expensive to manufacture conventional races having the required large diameter and small cross section.
Additionally, under increased load conditions, such as when thick sliver is carded and fed, the internal stresses in the conventional two-point contact ball bearing races increase. These forces tend to produce internal stresses on the bearings. As a result, either the bearings fail, or the ring gear travels in somewhat of an elliptical pattern instead of the desired circular pattern. When this occurs, the precise, predetermined adjustments between the knitting needles and doffing rolls change creating improper carding, feeding and knitting of the sliver fiber.
To avoid the problems associated with conventional ball bearings and races, conventional sliver knitting machines use a hydrodynamic bearing comprising a plurality of bronze friction elements immersed in oil between the ring gear and mounting ring. These bronze elements can be machined to close tolerances to fit within the bearing channel between the mounting ring and ring gear. However, hydrodynamic bearings create problems because the bronze, friction elements are immersed in oil and spaced from the mounting ring and ring gear to create an open area for the oil. When the sliver knitting machine is under a high load, such as when heavy sliver is carded and fed, the bronze elements move in an undesired elliptical pattern. Thus, the amount of force which can be exerted onto the ring gear and needles is limited, resulting in not only limiting the amount of sliver which can be fed to the knitting needles, but also limiting the number of feeds and the speed at which the sliver knitting machine can operate.
Another drawback of the conventional sliver knitting machine is the repeating occurrence of oil being blown out of the mounting channel. An annular air jet channel is mounted adjacent the mounting ring and a sliver feed mounting plate, also known as a card support ring, covers the channels and supports the sliver feed assemblies. The air jet channel provides an air flow to a plurality of air jet mechanisms forming a part of the sliver feed assemblies. A sealing compound positioned between the upper bed plate and the sliver feed mounting plate prevents air forced into the air jet channel from passing into the mounting channel and blowing the oil out of the channel. However, the sealing compound often degrades and contracts after continual machine use resulting in air blowing from the air jet channel into the mounting channel. As a result, the bearing oil is forced out of the mounting channel and the bearing assembly fails. A second, vented annular chamber or other means adjacent the air jet channel is preferred for allowing venting of that leaking air.